Management systems are well known for managing supply chains. Such management systems track elements from an initial stage, through intermediate stages (work-in-process stages), to a final stage. In manufacturing supply chain processes, the initial stage can be raw material, work-in-process can be assembly and the final stage can be finished goods. Warehouses to store raw material, semi-finished goods and/or finally finished goods are required at each stage of the process. Typically one or more suppliers provide manufacturing, warehouse and/or other services for processing and storing materials, semi-finished goods or other elements in a manufacturing processing chain from the initial stage, through the work-in-process stages to the final stage.
In a semiconductor industry example, the processing chain commences with wafers as initial elements and continues the processing over multiple work-in-process stages where the elements become dies that are assembled, tested and packaged to form devices at the final stage. In this example, the finished goods are tested chips that are packaged in single or multi-chip packages as the semiconductor devices. There can be one or more outside suppliers involved in this processing chain (“Out-sourcing”) or only internal departments providing all functions (“In-sourcing”) or a mixed use of the In-sourcing and the Out-sourcing. The completed semiconductor devices are ready to function as components in electronic equipment such as computers, cell phones or consumer electronic products. The semiconductor devices will enter another down-stream manufacturing chain where the components (initial stage) are sold to one or more buyers such as distributors, electronic equipment manufacturing service (EMS) companies or directly to the electronic equipment companies for assembly (work-in-process stage) and the final equipment will be produced (final stage). Frequently though, after an initial processing chain, one or more additional processing chains are required. For the same example, in the manufacturing of electronic equipment, semiconductor devices from a first processing chain are further processed in an electronic circuit board chain for forming circuit boards. Still again, after a second chain, third and additional processing chains may occur. For example, one or more electronic circuit boards are processed to form final electronic equipment such as a cell phone, computer or television.
Complex supply chain environments, such as in the semiconductor industry, present a number of difficulties. One difficulty results when multiple suppliers and buyers are participants in the processing chain (s), and each participant, whether buyer or supplier, tends to use different parameters, terminology, terms, conditions, formats, protocols and other information unique to the particular participant. These differences among participants result in information accuracy and exchange problems. Other problems occur when data is manually entered or otherwise processed by people. Human operations frequently cause data errors. Reports based upon human operations invariably have errors. Also, when information is stored and retrieved using remote data bases, the retrieval of data is often troublesome, inaccurate or not timely.
The information accuracy and exchange problems are aggravated when materials, goods, services and other elements from one stage are processed at downstream stages. Both upstream and downstream stages may be In-sourcing stages at one company or Out-sourcing stages existing with relationships among multiple buyers and suppliers. Regardless of whether In-sourcing or Out-sourcing occurs; visibility across the supply chain is required for efficient and economical supply chain management. For visibility to occur, the interrelationship among upstream and down stream stages requires an exchange of accurate, consistent and timely information.
The problems associated with the proliferation of different terminology, specifications, information exchange formats and protocols by participants in supply chains are well known. While a dominating buyer or a dominating supplier can demand conformance for its own business, the semiconductor manufacturing industry as a whole remains widely fragmented without much progress toward standardization. Although semiconductor industry efforts at standardization have occurred, for example Rosettanet, fragmentation is likely to exist for many years to come. Fragmentation exists, of course, in many other industries.
Management of the supply chain at the highest level relies upon, among other information, identity information for elements in all the stages of the supply chain. This identity information is used by companies including buyers and suppliers participating in the supply chain. In semiconductor manufacturing, the identity information has, in general, been limited to a wafer identifier (Wafer ID) for an individual wafer and a lot identifier (Lot ID) for an individual lot (a plurality of wafers). The identity information during work-in-process stages, as a result of manufacturing steps, often gets lost once a lot is split into sub-lots, after a wafer is cut into dies and/or after dies are packaged into semiconductor devices. When multiple dies are packaged together in a multi-chip packaged device, the identity information for the individual dies is typically lost.
Efforts have been made to track lots (and the related dies and devices) at each manufacturing step through the work-in-process stages. In the semiconductor industry, for example, wafers have been tracked with a Wafer ID using a static optical barcode. At the finished-goods stage, packaged devices are usually marked with new product identity information (typically loosing the Wafer bar code, any Lot ID, any Wafer ID and any individual device identity) before transfer to a subsequent processing chain or shipment to a buyer. The tracking of information is particularly difficult when tracking involves hierarchical elements.
Hierarchical elements are elements that have a hierarchical relationship to other elements in multistage and multistep processing. When a first element (for example, a semiconductor wafer) at one stage is divided into plural second elements in another stage (for example, semiconductor dies), the first element (wafer) is defined to be at a higher level in the hierarchy and the second elements (semiconductor dies) are defined to be at a lower level in the hierarchy. When a single element or plural second elements (semiconductor dies) are packaged to form a third element (a packaged part), the second elements (dies) are defined to be at a higher level in the hierarchy and the third element (package parts) is defined to be at a lower level in the hierarchy. Likewise, when plural third elements (semiconductor package parts) are combined to form a fourth element (a board with packaged dies), the third elements (package parts) are defined to be at a (higher) level in the hierarchy and the fourth element (board) is defined to be at a (lower) level in the hierarchy. All of the first, second, third and fourth elements have a hierarchical relationship to each other because the quality and other parameters affecting and characterizing the elements are correlated because the elements are subject to common processing, treatment or aggregation at different steps or stages. For the packaged-part elements described, tags are typically fixed to the packaged parts irrespective of where on or in the packaged element the tag is located.
Such correlated elements in this specification are defined to be hierarchical elements. For quality control, efficiency and other reasons, it is important to keep track of the hierarchy of elements undergoing multistage and multistep processing. Hierarchical tags are tags associated with hierarchical elements. In the semiconductor example, wafer tags are defined to be at a higher level than die tags and similarly die tags are at a higher level than package part tags (tags associated with packaged parts). The hierarchical history of a particular element is the history of the particular element and the history of the hierarchical elements with which the particular element is associated.
While tracking systems can attempt to track elements at an elemental level from the initial stage to the final stage of a chain, in actual practice, missing, incompatible and inaccurate information frequently results particularly when hierarchical elements are involved.
In systems in which a Wafer ID barcode is provided on each wafer, the Wafer ID is read with an optical reader at a wafer station. To read the Wafer ID, the optical reader causes an incident laser beam to impinge on the bar code and the incident beam causes a reflected beam which includes the bar code data. The incident laser beam, through human or machine control, must be aligned to accurately impinge on the Wafer barcode to cause a reflected beam to include the barcode information. The data coded in the barcode is processed by an optical reader to extract the barcode data. Such optical readers are directional and require careful alignment of the incident and reflected light beams. The alignment is frequently troublesome and misalignment results in unidentified wafers or other errors. Since the reflected light beam is typically weak, the distance between the barcode and the reader must be small to permit the barcode to be read. The distance generally required is in the range of from about 0.1 cm to about 50 cm. Barcode systems are adversely affected by dirt, dampness and other environmental conditions that are difficult to control and hence the identification accuracy is vulnerable to unfavorable environmental conditions.
Another problem associated with barcode identification systems is that only a Wafer ID is available from the barcode and any further detailed information is not available. When further information is wanted, the information is stored in a remote data base of the management system. To retrieve the local information of an element at any stage, the Wafer ID is provided to the data management system and a data base inquiry is made to obtain the local information. The local information is not attached physically to the element in the work-in-process stages and hence may not be readily accessible, may not be properly stored and may have been corrupted.
Where ID's are present at some stages of some chains, often the ID's are lost for subsequent chains so that no consistent linking of information is present for subsequent chains such as further processing and distribution chains.
In light of the foregoing problems, there is a need for improved systems for tracking elements from step to step, from stage to stage and from chain to chain and for accurately tracking elements commencing with an element start level using ID's that do not get lost.